Remote point notwithstanding, this is quite common, actually. Amazon's mean tenure is somewhere around 9 months and is well known for flogging their mandatory attrition curve; they also are known for having relatively forgiving hiring criteria to be constantly moving fresh blood through the system. Amazon backloads RSUs for this reason, and juniors routinely treat their employment there as a "tour of duty" before moving elsewhere, as the brand is still quite a strong stamp on the resumé.

Many parts of it can be a bad place to work. But it's a huge company. There are some parts doing cutting edge work as well that you won't get access to at other companies. But to your point, the likelihood that a junior engineer will get access to that is slim, and so your assertion holds.